The phone call came around 3:30 a.m. Saturday when Si Si Han was still in bed. It was a supervisor. The California Department of Transportation needed help at the Bay Bridge toll booth and asked if she could she come in as soon as possible.

“She just always lived to help other people,” Ryan Saw said by phone Monday morning. “That’s why she went in to work. If somebody needed something, she went.”

Han, 46, died Saturday when a box truck slammed into a line of cars and then into the No. 14 toll booth, a crash that the California Highway Patrol suspects was caused by driving under the influence. Daniel Berk, 32, of Foster City, has been arrested on suspicion of DUI and manslaughter and remains hospitalized with serious injuries.

Saw said he and Si Si met near Thailand just before he migrated to the United States with other family members in 1991, and that she adopted old-fashioned American work ethic immediately upon arriving in 2002.

Han, of San Lorenzo, worked for the California Department of Transportation for more than a decade after immigrating from Asia in 2002, and is survived by a 10-year-old daughter. Gov. Jerry Brown ordered flags at the state Capitol to be flown at half staff on Sunday.

“Her family was everything to her,” Saw said. “She did everything she could to support her daughter and the family.”

Thus, the reason she left the warmth of her bed for the chilliness of the booth.

“She wasn’t on the schedule,” Saw said. “She didn’t have to do it. But that’s who she was.”

“Our top priority is taking care of Mrs. Han’s family,” Caltrans spokesman Robert Haus said Sunday night. “It was nightmarish, seeing a normal workday turn into an incident like that. We are very grateful to the CHP and to our first responders.”

Two passengers in the truck and four people in other vehicles were hospitalized with serious injuries in the crash. Six cash/FasTrak lanes, two exclusive FasTrack lanes and two bus lanes remained closed until late Saturday night.

According to the CHP, the box truck from Monarch Truck Rentals hit the No. 14 toll booth, destroying it. Two passengers in the truck and four people in other vehicles were hospitalized with serious injuries, the CHP said.

As for Han’s family, Saw said they are doing the best they can moment by moment.